GOUGH ISLAND, a 25-square-mile mass of vol-
canic rock in the South Atlantic Ocean, is home
to millions of breeding seabirds, including the
entire world population of the Atlantic petrel
and all but a few pairs of the critically endan-
gered Tristan albatross. Ross Wanless first went
to Gough in 2003, as a doctoral candidate, after
other researchers had reported that alarmingly
few petrels and albatrosses were fledging chicks.
It was known that rats and cats, which humans
have introduced on islands all over the world,
prey heavily on seabirds. But there were no rats
or cats on Gough, only mice. Using video cameras
and infrared lights, Wanless recorded what the
mice were doing to the petrel chicks. “ The sun
went down,” he said, “and a mouse came out in
the petrel burrow. It hesitated and then started
nibbling on the chick. Other mice came, and I
witnessed this insane, disgusting attack. As the
blood started to flow, the mice got more and more
excited. At times, there were four or five of them
competing for the wound, lapping up blood and
going inside to eat the chick’s internal organs.”
Having evolved without terrestrial predators,
seabirds have no defense against mice. A petrel
in its inky-dark burrow
can’t even see what’s
happening to its chick,
and an albatross on its
nest lacks the instinct
to recognize mice as a
threat. In 2004, Wan-
less noted 1,353 breed-
ing failures among
Gough’s Tristan alba-
trosses, most of them
from predation, and
only about 500 suc-
cesses. In more recent
years, failure has been
as high as 90 percent.
Among all seabird spe-
cies on Gough, mice now kill two million chicks
every year, and many of these species are also
losing adults in the fisheries. Annual mortality
among adult Tristan albatrosses at sea has risen
to 10 percent—more than triple the rate of natural
mortality. Ten percent adult mortality plus 90 per-
cent breeding failure is a formula for extinction.
The calamitous decline in seabird populations
has many causes. Overfishing of anchovies and
Seabirds are
a poignant
combination of
vulnerability
and toughness.
An albatross
can’t stop
a mouse from
eating its
young.
other small prey fish directly deprives penguins
and gannets and cormorants of the energy they
need to reproduce. Overfishing of tuna, schools
of which drive smaller fish to the ocean’s surface,
can make it more difficult for shearwaters and
petrels to forage. Climate change, which alters
ocean currents, already appears to be causing
breeding failure among Iceland’s puffins, and
birds that nest on low-lying islands are vulnerable
to rising sea levels. Plastic pollution, particularly
in the Pacific Ocean, is clogging the guts of sea-
birds and leaving them hungry for real food. And
the resurgence of marine mammal populations—
in other respects, an environmental success
story—has resulted in more seals to eat young
penguins, more sea lions to crowd cormorants
out of their breeding sites, and more whales to
compete with diving birds for prey.
The number one threat to seabirds, however,
is introduced predators: rats, cats, and mice
overrunning the islands where they breed. This
is the bad news. The good news is that invasive
species are a problem with achievable solutions.
Organizations such as Island Conservation, a
nonprofit based in California, have perfected the
use of helicopters and GIS technology to target
predators with poisoned mammal-specific bait.
Animal lovers may grieve at the mass killing of
small furry mammals, but human beings have an
even greater responsibility to the species they’ve
threatened with extinction, however inadver-
tently, by introducing predators.
The most ambitious rodent-eradication effort
to date was mounted by the South Georgia Heri-
tage Trust. South Georgia island, 900 miles from
the Antarctic Peninsula, is the breeding ground
of perhaps 30 million seabirds; without rats and
mice, the island could easily host three times
that number. From 2011 to 2015, at a cost of more
than $10 million, three helicopters traversed
every ice-free area on South Georgia, dropping
bait. No living rat or mouse has been detected
on the island since 2015.
Similar efforts are now planned for Gough
Island, in 2019, and for South Africa’s Marion
Island in 2020. Mice came to Marion with whal-
ers and sealers in the 19th century. In the 1940s,
the South African government introduced cats
to control them, and the cats quickly went feral.
Instead of killing mice, they proceeded to deci-
mate the smaller seabird species nesting on the
island. (“Mice know exactly what a cat is,” Ross
Wanless explained. “Seabirds don’t.”) Marion’s
136 NATIONAL GEOGRAPHIC